Flashing not required at single-wythe masonry?

[Simonsays]

Folks,

We have been informed that single-wythe concrete masonry unit walls injected with expanding foam insulation do not require the code-recommended through wall flashing (1403.2/1405.3) with weepholes at lintels and door/window heads and base course or sills.

We think this is wrong.

What about you?

 

[Jobsaver]

Also, please include comments on same issue with brick veneers. I know what the code book says, and probably have yet another conundrum to deal with in my area, but in my limited travels about Arkansas, Texas, and Tennesee, I do not see weeps or thru-wall flashing on SFR's. What about you?

 

[Simonsays]

Refer to the following sections (these are from the 2006 IRC) regarding flashing and weepholes for brick veneer:

R703.1

fig. R703.7

fig. R703.7.2.2

R703.7.5

 

[peach]

Hi Simon..

I'd argue with whoever is telling you that.. the CMU itself is a porous concrete product subject to water intrusion... do the flashing.

 

[Mark K]

In California we use a lot of single-wythe CMU walls without through wall flashing without apparent problems. Of coarse we grout the cells and reinforce the walls. The through wall flashing would put a nice slip joint in the wall possibly causing problems for the structural strength of the wall in an earthquake.

In California an unreinforced masonry wall would be considered a hazard.

If CMU is porous putting horizontal flashing through the wall will do nothing to mitigate the moisture flow through the wall.

The flashing through the veneer masonry is part of a rain screen design approach that allows the water that gets trapped in the void between the two wythes to be channeled back outside. I do not see how this works with a single wythe wall? The applicant needs to define what his waterproofing strategy is.

 

[peach]

I've seen alot of stucco over CMU have failures because of flashing issues. All concrete products wick water. Direct the bulk out with the flashing.. air pressure will take care of the rest.. (which is why i don't like vapor barriers).

 

[Simonsays]

Great comments if the CMU remains hollows or is filled with porous grout. But the expanding insulating foam people say water can't wick thru.

There is no stucco or other exterior cladding or covering. The exterior of the CMU is the visible finish.

 

[Simonsays]

Now I'm being hit hard by pro-foamers (anti-flashers?) via email. They state that the code reads (1403.2) that "the wall envelope shall be constructed to prevent the accumulation of water WITHIN the wall assembly" and "flashing is a means for draining water that ENTERS the assembly." They are claiming that the expanding foam insulation will NOT let water within the wall.

Additional code section they cite (1405.3.2) requires flashing and weepholes "where anchored veneers are designed in accordance ..." and in this case, there are NO anchored veneers!

 

[KZQuixote]

Now I'm being hit hard by pro-foamers (anti-flashers?) via email. They state that the code reads (1403.2) that "the wall envelope shall be constructed to prevent the accumulation of water WITHIN the wall assembly" and "flashing is a means for draining water that ENTERS the assembly." They are claiming that the expanding foam insulation will NOT let water within the wall.Additional code section they cite (1405.3.2) requires flashing and weepholes "where anchored veneers are designed in accordance ..." and in this case, there are NO anchored veneers!

That's ridiculous. The water will still move through the masonry just as before. However I'm wondering where you would use a through the wall flashing on a single wythe wall. Typically these walls are surface barrier systems and require no flashing.

Bill

Later: I reviewed the code sections and the exceptions to 1403.2 are clear. "A weather-resistant exterior wall envelope shall not be required over concrete or masonry walls designed in accordance with Chapters 19 and 21, respectively." Nothing in those chapters would require weep holes or any through the wall flashings in single wythe masonry. And unless the assembly includes a weather-resistant wall envelope there would be nowhere to use a flashing or any weep holes.

 

[Sandman]

http://masonrysystems.org/pdf/Guidelines-for-Single-Wythe-Walls.pdf

Flashing & weepholes are recommended regardless of insulation.

 

[conarb]

Chicago is having an epidemic of leaking, deteriorating buildings, you should read this.

 

[TimNY]

With open cell foam water will penetrate. I guess it would be a practical exercise to see if it accumulates.

Water will not penetrate the closed cell foam, as far as I know.

If they are going to bombard you with emails, how about they specify what type of foam and what density they propose to use. I would read the manufacturer's instructions for the specific foam proposed.

It' kinda like saying "I'm going to build this girder out of wood.. See! The code says I can use wood!"

 

[Code Neophyte]

Slow getting back to this thread. Go here: http://midwestproductsgroup.com/index.php/categories/Commercial-Masonry/Technical-Notes-and-Details , click on 'NCMA', then 'e-Tek' for the NCMA Tek notes. Go to #19 - Water Penetration Resistance. There's a great section detail there showing a proper flashing detail for single-wythe walls.